Mastitis is the inflammation of mammary tissues, and most of its causes are due to the infection of bacteria, such as Staphylococcus aureus, Escherichia coli, Streptococcus, and Pseudomonas aeruginosa. Particularly, mastitis in cows is an important problem for dairy farmers, as described below.
Mastitis is roughly divided into clinical mastitis and subclinical mastitis (also referred to as nonclinical mastitis). In the clinical mastitis, macroscopic abnormalities, such as the red swelling, fever, and pain of the breast or the contamination of milk with clots are observed, whereas in the subclinical mastitis, inflammation occurs in the mammary gland without abnormalities as in clinical mastitis. The subclinical mastitis is much higher in the percentage of occurrence, and about 25 to 50% of milking cows are said to suffer from the disease.
As to the onset of mastitis in cows, it is the present situation that there is not taken a sufficient countermeasure of prevention of mastitis before onset or therapy of cows affected with mastitis, which is a large problem in the milk industry. According to “the number of cows having disease accidents classified by disease types” reported in Statistical Tables of Livestock Mutual Relief, 2009 in Japan, 30% of about 1,410,000 cows had urinary diseases, of which around 90 percent had mastitis. Also in the number of cows having death or disuse accidents classified by disease types, 9% of about 160,000 had urinary diseases. Thus, in fiscal year 2009 alone, cows affected with mastitis were about 420,000 in number, and the number of discarded cows amounts to 15,000. In addition, the onset of mastitis reduces milk quality and milk yield, resulting in incalculable economic loss. Therapy for mastitis is carried out by administering antibiotics; however, such therapy does not often result in a complete cure and there is at present no method other than isolation. Even if the antibiotic administration led to a complete cure, milk during its administration cannot be shipped; thus, economic loss due to mastitis is said to be estimated to be about one hundred billion yen in Japan. In addition to the direct economic loss, the labor load and the prescription charge associated with the therapy of cows infected with mastitis are not negligible. Further, side effects are conceivable, such as that dairy cows once having the onset of mastitis have an extremely high probability of having the onset of mastitis during the subsequent lactation period after delivery and that dairy cows affected with mastitis have delayed estrus. As such, in addition to a means for prevention or effective therapy of mastitis being sought in the milk industry, there is an urgent need for the establishment of a technique for preventing, or suppressing the recurrence of, mastitis.
Various proposals have previously been made for the prevention or therapy of mastitis in ruminant animals, such as cows. Among these proposed preventive or therapeutic agents, some examples using microorganisms for the prevention or therapy of mastitis have been in particular reported.
For example, Patent Literature 1 discloses a composition for the prevention or therapy of mastitis in cows, comprising a culture composition obtained from a culture of a microorganism belonging to the genus Aureobasidium as an active ingredient.
Patent Literature 2 discloses a composition for the prevention or therapy of livestock mastitis, comprising viable baker's yeast cells or their contents as an active ingredient.
Other examples of the use of a viable bacterial agent in dairy cows include the use of Natokin-L (lactic acid bacterium and Bacillus subtilis), Miyairi bacterial powder (butyric acid bacterium), Biosuri (lactic acid bacterium, saccharifying bacterium, and butyric acid bacterium), and Bovactin (lactic acid bacterium and butyric acid bacterium) for the prevention/therapy of simple diarrhea (Non Patent Literature 1). Table 2 in this literature describes that the incidence of mastitis was decreased by the use of a viable bacterial agent; however, it is not shown what the viable bacterial agent was. In this connection, among the viable bacterial agents listed in Table 1 of the literature, “Biosuri” is now used in 80 to 90% of the cases of viable bacterial agent administration to dairy cows; thus, the viable bacterial agent used in Table 2 is presumed to be probably “Biosuri”. Viable bacteria agents including Biotop (Bacillus subtilis) are known to have effects, such as drastically decreasing the occurrence of tympania, stimulating appetite, and rendering the hair glossy, as well as effects, such as decreasing the number of cows excreting Salmonella (Non Patent Literature 2).
In addition, the same applicant as the applicant of this application teaches the use of viable cells of Bacillus subtilis as an agent for improving the efficiency of feed utilization for ruminant animals (Patent Literature 3). The improvement of the utilization efficiency in this literature is the improvement of the efficiency of digestion absorption, which improves milk yield and milk quality in dairy cows. The same applicant as the applicant of this application also teaches a feed additive prepared by mixing Bacillus subtilis strain C-3102 with vitamins, minerals, amino acids, and the like (Patent Literature 4). Furthermore, Patent Literature 5 describes the use of Bacillus subtilis for reducing the growth of enteric pathogenic bacteria in animals, such as ruminant animals. However, Patent Literatures 3, 4, and 5 do not describe that Bacillus subtilis is useful for the prevention and therapy of mastitis in cows.